1. Field of the Invention
The present invention relates to a keyboard apparatus in which fitting of an incorrect key-top on a key-switch body in the type of the key-top and fitting direction thereof is avoided when each key-top corresponding to each of plural kinds of the key-switch bodies arranged on a keyboard base is fitted thereto.
2. Description of the Related Art
On a keyboard base of a computer, a word processor, etc. numerous key-switches 100 . . . are arranged, as shown in FIG. 6 for example. To these key-switches 100 . . . are fitted key-tops for being pushed by a finger having various shapes in a top view thereof, such as roughly rectangular shapes, half-size shapes, crosswise shapes, odd size L-shapes, etc. Moreover, when taking only the half size shaped key-switch (referred to "a half key" below), as an example, there are subtle differences in the shapes thereof in accordance with arranged positions thereof, as shown by key-switches 100a, 100b, 100c, 100d, 100e, and 100f.
The key-switch generally comprises a key-top 110 and a key-switch body (referred to simply "a body" below) 120, as shown in FIGS. 7A and 7B, as an example. The key-top 110 comprises a top plate 11 being pushed by a finger, a stem portion 12 extending below the top plate 11 through an axis "X" of the key-top 110, a hook portion 13 disposed in the both sides of the stem portion 12 sandwiched therebetween, and a side wall 14 extending below the periphery of the top plate 11.
The body 120 comprises a housing 21 accommodating the body 120, a rubber spring 22 connected to the bottom end of the stem portion 12 having a shape of a bowl inverted on the surface, and a membrane switch 24 disposed underneath a pushing portion 23 of the rubber spring 22, being formed below the center apex of the rubber spring 22. In the housing 21 formed are a socket 25 into which the stem portion 12 is vertically slidably inserted, and a hook holding hole 26 with which the hook portion 13 engages so that the key-top 110 cannot be pulled out from the body 120.
In order to fit the key-top 110 to the body 120, the key-top 110 is oriented relative to the body 120 so that the hook portion 13 engages with the hook holding hole 26 relative to the axis "X"; the end of the stem portion 12 is inserted into the socket 25; and the key-top 110 may be only pushed downward in this state. At this time, the stem portion 12 is connected to the rubber spring 22 by fitting an annular portion 29 of the rubber spring 22 formed upward protrudingly from the center apex thereof into the end of the stem portion 12; simultaneously the end portion of the hook portion 13 is inserted into and brought into engagement with the hook holding hole 26 so as to be not pulled out therefrom; and fitting is completed.
In this key-switch, when the top plate 11 is pushed by a finger, the stem portion 12 slides downward in the socket 25 such that the end of the stem portion 12 pushes the rubber spring 22 downward to buckle it. Thereby, the membrane switch 24 is pushed by the pushing portion 23 so as to be brought into conduction. When the finger is separated from the top plate 11, the key-top 110 returns to the original position thereof by a repulsion force of the rubber spring 22 to thereby turn the membrane switch 24 off.
When the keyboard is assembled, each key-switch body having a specific function is arranged at and assembled in the corresponding position of the keyboard in advance; each key-top corresponding to the body is fitted thereto; and a specific symbol such as an alphabet is printed afterward on the top plate surface of the key-top by a laser for example.
When key-tops having distinct different shapes and sizes are assembled, fitting thereof to each of corresponding bodies is comparatively easy due to easy recognition thereof. However, in order immediately to recognize key-tops having subtle differences in the shapes thereof, as half keys 100a to 100f, to fit them to corresponding bodies, considerable attention is needed, such that key-tops of the different type are prone to be incorrectly fitted. Once the different type of key-top is incorrectly fitted, it cannot be pulled out because the hook portion 13 engages with the hook holding hole 26 as described above, resulting in decreasing productivity so that it is eliminated from the production line as a failed product, for example.
Even the same type of key-top generally has a shape being unsymmetrical between back and foreground sides of the keyboard surface, so that fitting of key-tops inverting back and foreground sides has been done.